1. Field of the Invention
This invention relates to a magnetic head utilizing a magnetic reluctance effect element for converting magnetic signal fields in magnetic tapes or disks to electric signals and a method for making such a magnetic head.
2. Description of the Prior Art
Attention has been recently directed to a magnetic resistive element (called "MR element" hereinafter) which can be used as a material for magnetic heads, because it can be relatively simply manufactured and is suitable for integration. Various magnetic heads having such MR elements have been developed. FIG. 1 shows a typical MR magnetic head of the simplest structure which comprises an MR element 101 formed in a firm by the use of a film depositing method such as resistance heating deposition, electron beam deposition, spattering, plating, chemical vapor deposition or other methods. The MR element is shaped by means of photolithography which has been well known in the art as a technique for processing integrated circuis (IC). The MR element can be shaped also by mask vapor deposition. The MR element has a suitable thickness in the range of 0.02-0.1 .mu.m which is actually determined by taking account of its chemical stability and electric resistance. The MR element is made of permalloy containing about 80% of nickel of nickel-cobalt alloy. The so obtained MR element has a resistance taper rate of 1-2% in the magnetic field of 5-100 oersteds.
FIG. 1 also shows lead wires 102a and 102b which are connected with the opposite ends of the MR element. The other ends of the lead wires are connected with a circuit (not shown) for reading variations in voltage when a constant current is supplied to the MR element. These lead wires are made of aluminium, copper, gold or other conductors by the use of similar film depositing method and then shaped by the use of photolithography.
The resistivity of the film-like MR element is in the range of 20 to 30 .mu..OMEGA..multidot.cm while that of the film-like lead wires is in the range of 2.5 to 4 .mu..OMEGA..multidot.cm. The resistivity of the lead wires may be even smaller if they are of aluminium, gold and copper. Roughly calculating, the lead wires becomes about 1/150 of the MR element in resistivity when the MR element has a thickness of about 0.05 .mu.m and the lead wires have a thickness of about 1 .mu.m. This means that almost the total amount of supplied current is fed to the MR element through the lead wires 102a and 102b.
The magnetic head shown in FIG. 1 also includes a substrate 103 of glass, silicon or other materials on which the MR element 101 and the lead portions 102a, 102b are secured. Reference numerals 104 and 105 designate a recording medium and a base to which the recording medium is applied, respectively. Arrows 106 denote directions of magnetization lines which are recorded in the recording medium.
The MR element 101 is moved in contact with the magnetically recording surface of the recording medium so that the resistance thereof will be varied depending upon magnetic signal fields produced from the magnetization lines 106 of the recording medium. If a constant current is supplied to the MR element, such variations in resistance would appear at the lead wires in the form of variations in voltage corresponding to the recorded information. Such an MR element has many features in that it has a temperature coefficient smaller than that of prior art Hall element, that it can be simply manufactured, that it has a simple structure suitable for integration, and so on. Moreover, it has an advantage in that magnetic signals can be properly reproduced even at a variable relative speed without depending on the speed relative to the recording medium as in induction type heads.
However, such a useful MR element also has the following disadvantages:
(1) Although the MR element has a simple construction, a complicated process must be carried out for making it. In other words, the process comprises various steps of forming the lead portions in addition to the MR element in a film-deposition manner, shapingthe lead portions by the use of an etching technique and then shaping the MR element by further etching.
(2) If the lead members are made of copper or gold, the permalloy material of the MR film is significantly affected in etching the lead portions. This results in difficulties in controlling the magnetic characteristics.
(3) If lead members of aluminium, copper or gold are deposited in a film on the MR film, the magnetic fields present upon heating, chemical reaction and vapor-deposition, particularly in spattering cause substantial variations in the magnetic characteristics of the MR film, already formed, such as direction and magnitude in the magnetic anisotropism, electric resistivity, resistance taper rate, saturated magnetic flux density and coercive force. This effect causes a dispersion in the sensor characteristics.